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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 34 (1969), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: SUMMARY– Acid and enzymatic demethylation procedures suggest that the change in molecular weight during methylation is a result of depolymerization and that a change in the percent methoxyl groups probably has very little effect on the change in molecular weight during methylation or demethylation with pectins having an ester content between 60% and 95%.Samples of a commercially prepared citrus pectin were acid washed, dissolved and neutralized to different levels with dilute NaOH. These samples were treated with isopropanol to yield an open gel-like precipitate, the alcohol was replaced with ether and the pectin treated with diazomethane at 〈 −30°C. The samples methylated to 70%, 85% and 95% had molecular weight values which decreased with increasing degrees of esterification. Molecular weight was determined by measuring the viscosity of a 0.1 % sol in 1 % Calgon.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 32 (1967), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A sample of a commercial slow-set citrus pectin was separated into its major fractions on diethylaminoethylcellulose columns using increasing concentrations of NaH2PO4 solution as the eluent.The fraction eluted with the lowest concentration of NaH2PO4 had the highest methoxyl content, and later fractions, obtained with progressively increasing NaH2PO4 concentrations, showed progressively lower methoxyl values. The per cent esterification and equivalent weight also decreased in a similar manner. This decrease in methoxyl content from one fraction to the next was accompanied by an increase in setting times and jelly grades. By using a viscosity measurement in 1% Calgon, no regular change in molecular weight from one fraction to the next could be observed and none of the fractions had a molecular weight as high as the original pectin.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 33 (1968), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: SUMMARY— A series of samples with percent esterification ranging from 73.7 to 28.6 was prepared under acid conditions at room temperature from lemon peel pectin that had been precipitated with aluminum. Molecular weight, as determined by viscosity in 1% Calgon, and galacturonic acid content remained unaltered during demethylation while equivalent weight decreased. Setting time increased until an ester content of around 50% was reached. At lower ester values setting time decreased again.Maximum jelly grades were obtained at an ester content of ca. 45%. However, at this ester level the pH at which a high jelly grade was obtained was very low and the grade decreased very rapidly as the jelly pH was increased to values above pH 2.2. The maximum grade obtained with a particular sample decreased and the pH at which this maximum grade could still be obtained increased as the ester content was increased above ca. 45%. Below this ester level, the maximum grade as well as the maximum pH at which this grade could be obtained decreased with ester content.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 1945-06-29
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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